This invention relates to novel tetrahydrocarbyl phosphonium salts and the use of these and other salts to prepare novel epoxy resins. More particularly, the resulting resins incorporate the phosphonium salts or derivatives thereof.
Epoxy resins have long been produced by the reaction of a vicinal epoxide with a compound bearing phenolic hydroxyls in the presence of a catalyst in a so-called advancement reaction. A variety of catalysts have been reported in the art, including tertiary amines, quaternary ammonium halides, phosphonium halides, phosphonium carboxylates and the like. Processes for using these catalysts, as well as stoichiometric reagents, have been detailed in U.S. Pat. Nos. 2,216,099; 2,633,458; 2,658,855; 3,377,406; 3,477,990; 3,547,881; 3,547,885; 3,569,374; 3,694,407; 3,738,862; 3,948,855; 4,048,141; 4,177,216 and 4,302,574. Canadian Patent No. 893,191, German Patent DT Nos. 2,206,218 and 2,335,199, the texts Handbook of Epoxy Resins by H. Lee and K. Neville, McGraw-Hill (1967) and Epoxy Resins Chemistry and Technology, edited by C. A. May and Y. Tanaka, Marcel Decker, Inc. (1973) are also of interest.
The use of certain phosphonium trifluoroacetate salts as advancement catalysts for epoxy resins is disclosed in U.S. Patent Application Ser. No. 391,094, filed June 23, 1982, now abandoned. It is disclosed therein that these phosphonium salts may bear hydroxyphenyl or thiophenyl moieties. It should be noted that the hydroxyphenyl and thiophenyl were proposed by one of the inventors of the instant invention common to the above-identified application.
In general, the prior art catalysts or derivatives thereof can be extracted from the resulting epoxy resin product. In certain applications the presence of an extractable salt is undesirable. Accordingly, it would be desirable to prepare advanced epoxy resin compositions which contain reduced quantities of extractable residue from the catalyst.